What is the required slack in horizontal cables within a telecommunications room (TR)?

The correct answer highlights the need to provide enough slack in horizontal cables to ensure they can easily reach the farthest corner of the telecommunications room, considering the layout and potential future changes. This flexibility is crucial for maintaining cable management and accessibility, accommodating any adjustments that may be necessary as equipment is added or rearranged.

Having sufficient slack allows technicians to manipulate the cables without putting undue stress on them, which is vital for maintaining signal integrity and longevity. In contrast, the other options specify fixed distances that might not account for the actual configuration of the telecommunications room or changes in equipment or pathways, making them less adaptable to real-world scenarios. Therefore, prioritizing flexibility and ensuring the cables can reach various points within the TR is essential for effective network management.